Narrowband sensors based on plasmonic metasurfaces integrated on piezoelectric plates

ABSTRACT

An optical detector system includes a light source configured to emit light having a frequency spectrum and modulated in time, and an optical detector configured to detect an intensity of the light at a wavelength range within the frequency spectrum. The optical detector includes a piezoelectric layer, a first metal layer coupled to a first surface of the piezoelectric layer, a second metal layer coupled to a second surface of the piezoelectric layer, and a plasmonic metasurface coupled to the first metal layer and configured to absorb the light at the wavelength range, the plasmonic metasurface including metal structures and a dielectric layer disposed on the first metal layer. The optical detector system further includes a voltage detector coupled to the first metal layer and the second metal layer, the voltage detector configured to detect a voltage at a frequency of the modulated light.

BACKGROUND

A metasurface is an artificially made material, also referred to as ametamaterial, that includes structures of symmetrically arrangedgeometric patterns having sub-wavelength dimensions with respect to aportion of the electromagnetic spectrum. A plasmonic metasurface is atype of metasurface that exhibits negative real permittivity and, underconditions of electromagnetic excitation, can create surfacecharge-density oscillations known as surface plasmon-polaritons (SPPs).Plasmonic metasurfaces are formed by metals or metal-like materials,such as a combination of metallic and dielectric materials, and containsubwavelength-scaled structures that are distributed on or under thesurface. The structures may have similar or different geometries and maybe repeated and spaced across a layer to alter the behavior ofelectromagnetic waves, thereby generating the SPPs. For example, thestructures may be separated circular, square or cross-like metal patchesthat are placed on a dielectric layer. A plasmonic metasurface can bedesigned to interact with an electromagnetic wave in a certain lightspectrum, such as visible or infrared (IR) light, to absorb or reflectlight at a certain wavelength or frequency.

SUMMARY

In accordance with at least one example of the description, an apparatusincludes a first metal layer, a piezoelectric layer on the first metallayer, a second metal layer on the piezoelectric layer, a plasmonicmetasurface on the second metal layer, the plasmonic metasurfaceincluding a dielectric layer and metal structures, and the apparatusfurther including a voltage detector coupled to the first metal layerand the second metal layer.

In accordance with another example of the description, an optical deviceincludes a plasmonic metasurface configured to absorb an incident lighthaving a frequency spectrum and modulated in time, a first metal layercoupled to the plasmonic metasurface, a piezoelectric layer coupled tothe first metal layer, a second metal layer coupled to the plasmonicmetasurface, and a voltage detector coupled to the first metal layer andsecond metal layer, the voltage detector configured to detect anamplitude of an electrical signal modulated in time according to themodulated incident light.

In accordance with another example of the description, an opticaldetector system includes a light source configured to emit light havinga frequency spectrum and modulated in time, and an optical detectorconfigured to detect an intensity of the light at a wavelength rangewithin the frequency spectrum, the optical detector including apiezoelectric layer, a first metal layer coupled to a first surface ofthe piezoelectric layer, a second metal layer coupled to a secondsurface of the piezoelectric layer, a plasmonic metasurface coupled tothe first metal layer and configured to absorb the light at thewavelength range, the plasmonic metasurface including metal structuresand a dielectric layer disposed on the first metal layer, and theoptical detector system further including a voltage detector coupled tothe first metal layer and the second metal layer, the voltage detectorconfigured to detect a voltage at a frequency of the modulated light.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a light detector system, in accordance withvarious examples.

FIG. 2 is a graph of light intensity of emitted light in the lightdetector system of FIG. 1 , in accordance with various examples.

FIG. 3 is a diagram of an optical device, in accordance with variousexamples.

FIG. 4 is a graph of absorption of incident light on the optical deviceof FIG. 3 , in accordance with various examples.

FIG. 5 is a graph of measured voltage responsive to incident light onthe optical device of FIG. 3 , in accordance with various examples.

FIG. 6A is a diagram showing a top view of an optical device includingmultiple sensor units, in accordance with various examples.

FIG. 6B is a diagram showing a cross section view of the optical deviceof FIG. 6A, in accordance with various examples.

FIG. 7A is a diagram showing a top view of an optical device includingmultiple sensor units, in accordance with various examples.

FIG. 7B is a diagram showing a cross section view of the optical deviceof FIG. 7A, in accordance with various examples.

FIG. 8 is a graph of absorption of incident light on an optical deviceincluding multiple sensor units, in accordance with various examples.

FIG. 9 is a diagram of a cross section of a sensor unit anchored at twoopposite sides, in accordance with various examples.

FIG. 10 is a graph of voltage to temperature sensitivity of the sensorunit of FIG. 9 , in accordance with various examples.

FIG. 11 is a diagram of a cross section of a sensor unit anchored atfour sides, in accordance with various examples.

FIG. 12 is a graph of voltage to temperature sensitivity of the sensorunit of FIG. 11 , in accordance with various examples.

FIG. 13 is a circuit diagram of an optical detector system includingmultiple sensor units, in accordance with various examples.

FIG. 14 is a graph of multiple light absorption profiles for an opticaldevice including multiple sensor units, in accordance with variousexamples.

FIG. 15 is a flow diagram of a method for light detection in an opticaldetector system, in accordance with various examples.

FIG. 16 is a block diagram of a hardware architecture for processingsignal data, in accordance with various examples.

DETAILED DESCRIPTION

Optical detectors, which may also be referred to as light detectors, aretypes of devices that detect light at a specific frequency or wavelengthrange. The detection includes absorbing a portion of light radiationthat illuminates a surface of the detector and converting it into asignal, such as an electrical signal, which can be measured andanalyzed. Light that illuminates or is projected onto a surface may alsobe referred to as incident light. Analysis of the measured electricalsignal is useful to infer the characteristics of a sample exposed to thelight radiation. The characteristics of the sample may include the type,composition, or density of substances in the sample. For example,optical detectors can be useful as gas or fluid detectors with one ormore light sources having a frequency spectrum, such as infrared,visible light, or ultraviolet laser sources. Optical detectors mayinclude various materials and layers designed for specific detectionapplications.

An optical detector may include a plasmonic metasurface that isengineered according to the application. This may involve the plasmonicmetasurface achieving a peak in absorption at a wavelength of light andsubstantially low or no absorption away from that wavelength. Suchresponse is referred to as a resonance response, and the wavelength atthe peak absorption is referred to as the resonance wavelength. Theresonance response may provide a filtering effect of the incident lightwhere light may be absorbed within a relatively narrow wavelength rangewith respect to the frequency spectrum of the emitted light. Plasmonicmetasurface design includes determining the spacing and size ofstructures dispersed across the plasmonic metasurface, for instance inthe form of a two-dimensional (2D) array. To achieve detection, theplasmonic metasurface may be combined with other materials and layersthat are stacked over one another and anchored with low thermal couplingto a base, such as a silicon (Si) substrate or other form of substrate.

Responsive to projecting incident light on the plasmonic metasurface,the incident light radiation may interact with the plasmonic metasurfacecausing energy oscillation at the surface. The energy oscillation may bereferred to as a plasmon. The energy generated at the plasmonicmetasurface which undergoes the plasmon effect can propagate intosublayers in the detector and is useful for detection. The metamaterialmay be coupled to a piezoelectric layer and metal layers on thesubstrate. The piezoelectric layer is an active layer that expands orcontracts, responsive to absorbing the light radiation from theplasmonic metasurface, and converts the thermally-induced deformationinto an electric signal.

The description provides various examples of combining plasmonicmetasurfaces with a piezoelectric layer in an optical detector. Thecombination may provide for light detection with multi-sensor capabilitywhich is useful for characterizing multiple samples. The variousexamples of the optical detector design may detect multiple gasconcentrations in a medium with a broadband light source. The design canhave a compact form factor, and therefore may have a reduced cost andenergy consumption in comparison to other approaches. The opticaldetector may include multiple plasmonic metasurfaces disposed on apiezoelectric layer and metal layers. Each plasmonic metasurface on thepiezoelectric layer may operate as a sensor unit in the optical detectorand may be designed for absorbing a broadband incident light at acorresponding resonance wavelength. The optical detector may alsoinclude contacts that anchor each sensor unit to the surroundingcomponents in the optical detector package. The anchor contacts mayprovide structural support with limited thermal coupling of the sensorunits.

The broadband light from the light source, which may have an IR orvisible frequency spectrum, may be modulated at a certain frequencywithin the spectrum. The modulated light may be absorbed by the opticaldetector, and cause the piezoelectric layer to contract and expandperiodically in time due to light modulation. Light energy absorption inthe piezoelectric layer may provide an electric signal which may bemeasured in the form of voltage. The amplitude of the measured voltagemay be proportional to the amount of absorbed light at the resonancewavelength of each plasmonic metasurface of a sensor unit in the opticaldetector.

The sensor units can be coupled in parallel through respectivetransimpedance amplifier circuits, and a multiplexer may couple theamplifier circuits to a processor to enable analyzing the voltage at thepiezoelectric layer. The analysis may be based on the relation betweenthe voltage amplitude detected from the piezoelectric layer and thetemperature reached by the piezoelectric layer caused by lightabsorption. Thus, the detected voltage level can be linked to theamplitude of the incident light that is absorbed by the opticaldetector, and a change of measured voltage can be correlated with achange of temperature and therefore light amplitude. The change in lightamplitude at the optical detector can be attributed to a characteristicof the sample, such as volume or concentration of a gas, exposed to thelight before absorption. Further, the voltage to temperature sensitivitycan be increased by adding more anchor contacts to the sensor units, asdescribed below.

FIG. 1 is a block diagram of a light detector system 100, in accordancewith various examples. The light detector system 100 may include a lightsource 110 and an optical detector 120 separated by a space 121. Thelight source 110 may be any light emitting device that emits a lightbeam 134 directed toward the optical detector 120. For example, thelight source 110 may be a laser that emits the light beam 134 in thevisible spectrum or the infrared (IR) spectrum. The optical detector 120may be positioned in front of the light source 110 to detect at least aportion of the emitted light beam 134 that is incident on the surface ofthe optical detector 120. The optical detector 120 may be designed toabsorb a portion of the light beam 134 within a wavelength or frequencyrange which falls in the light spectrum of the light source 110. Theintensity or amplitude of the absorbed portion of the light beam 134 maybe detected by the optical detector 120. The components of the opticaldetector 120 may be encased in a package to protect the optical detector120.

A sample 135 to be analyzed may be disposed in the space 121 between thelight source 110 and the optical detector 120 such that the sample 135is exposed to the light beam 134. The absorbed portion of the light beam134 may be collected at the optical detector 120 and converted into anelectric signal, such as a voltage, which may be measured and analyzedto infer characteristics of the sample 135. For example, the sample 135may be a fluid, a gas, or multiple gases. The characteristics of thesample 135 may include the chemical composition, density, concentration,or molecular size of the sample 135. The light detector system 100 mayalso include a chamber 140 for holding or containing the sample 135. Thechamber 140 may include openings in front of the light source 110 andthe optical detector 120 to allow the passing of the light beam 134 fromthe light source 110 to the optical detector 120 through the chamber140. In an example, the chamber 140 may include a first opening 142 anda second opening 143, separated by a distance (d). The first opening 142may be an inlet for injecting the sample 135 into the chamber 140, andthe second opening 143 may be an outlet for releasing the sample 135from the chamber 140. The chamber 140 may include a lens 145 foraligning and projecting the light beam 134 toward the optical detector120.

The light detector system 100 may also include a processing system 150electrically coupled to the optical detector 120. The processing system150 may receive electrical signals from the optical detector 120,responsive to the optical detector 120 absorbing a portion of the lightbeam 134 from the light source 110. The electrical signals may bemeasured, such as via a voltage detector, and analyzed to determine thecharacteristics of the sample 135. The processing system 150 may includea processor (not shown) for processing the electrical signals based onstored data or models for characterizing the sample 135. For example,the processing system 150 may be a computer system including aprocessing chip (not shown) and a storage medium (not shown).

FIG. 2 is a graph 200 of light intensity of emitted light in the lightdetector system 100, in accordance with various examples. In the graph200, the x-axis represents a range of wavelengths of the emitted lightin micrometers (μm) and the y-axis represents a relative scale of thepower values of the emitted light beam 134 by the light source 110. Thewavelength range of the x-axis is between approximately 1 and 7 μm,which may be part of the IR spectrum. The light intensity is representedby a curve 201 and corresponds to the radiation power of the light beam134 emitted by the light source 110 in the IR spectrum. The wavelengthrange may overlap at least partially with a wavelength region 202centered at approximately the resonance wavelength (at approximately 4.5μm) of a plasmonic metasurface in the optical detector 120. Accordingly,the optical detector 120 may absorb a portion of the light beam 134 thatis useful for detection of the light in the wavelength region 202.

FIG. 3 is a diagram of an optical device 300, in accordance with variousexamples. The optical device 300 may be a light sensing device capableof absorbing incident light 301 on a surface of the optical device 300.Absorbing a portion of the incident light 301 may be useful fordetecting the intensity or amplitude of the incident light 301 in thewavelength region 202. For example, the optical device 300 may be partof the optical detector 120 and may provide an electrical signalresponsive to absorbing a portion of the incident light 301. Theincident light 301 may be emitted from a light source 302 having afrequency spectrum in the IR region, such as the light source 110 whichemits the light beam 134. The amplitude of the incident light 301 in theIR spectrum may also be modulated in time by varying the power of thelight source 302 between different power levels according to a time wavepattern or by switching the light source 302 on and off periodically intime.

The optical device 300 may include multiple layers and materialsdesigned to increase the absorbed amount or portion of the incidentlight 301 within a certain wavelength range. Increasing the amount ofabsorbed light may increase the signal-to-noise ratio in a lightdetection system and therefore allow for more accurate detectionresults. The optical device 300 may include a patched metal layer as aplasmonic metasurface 310, a piezoelectric layer 330, a first metallayer 332 between the plasmonic metasurface 310 and the piezoelectriclayer 330, and a second metal layer 332 under the piezoelectric layer330.

The plasmonic metasurface 310 may include a one-dimensional (1D) or 2Darray of structures 342 disposed on or in a dielectric layer 344. Forexample, the structures 342 may correspond to a grid of metal patchesequally spaced on the dielectric layer 344. In another example, theplasmonic metasurface 310 may include a grid of equally spaced gaps in ametal layer (not shown). The gaps may be empty gaps or may be filledwith a dielectric or other material or a combination thereof. Thestructures 342 may have various geometric patterns, sizes, and spacing.For example, the geometric patterns may include square, round, slit, orcross patterns. The spacing of the structures 342 may determine theresonance response of the plasmonic metasurface 310 responsive toabsorbing a portion of the incident light 301 at a wavelength rangenarrower than the IR spectrum. The dielectric layer 344 may include adielectric material transparent to the incident light 301 in at least aportion of the IR spectrum. For example, the dielectric layer 344 may bea silicon oxide (SiO₂) layer or any other suitable dielectric material.

The piezoelectric layer 330 may be formed from a piezoelectric material.An example of a piezoelectric material is a crystal material capable ofconverting mechanical energy into electrical energy. For example, thepiezoelectric layer 330 may be an aluminum nitride (AlN) layer and thefirst and second metal layers 332 may be molybdenum (Mo) layers. Thepiezoelectric layer 330 may deform in the contour or thicknessdirections responsive to absorbing the light energy from the plasmonicmetasurface 310, which may provide heat energy in the piezoelectriclayer 330. The heat energy may be converted by the piezoelectric layer330 into electric energy. The electric energy may be collected bycoupling electrodes 307 and 309 to the first and second metal layers332, respectively. The transferred electric energy may be measured as anelectrical signal, such as a voltage 311. For example, the electrodes307 and 309 may be coupled to the first metal layer 332 between theplasmonic metasurface 310 and the piezoelectric layer 330, and to thesecond metal 332 under the piezoelectric layer 330. The optical device300 may also include contacts (not shown) that anchor the plasmonicmetasurface 310, the metal layer 320, and the piezoelectric layer 330 tothe surrounding substrate in a component package that includes orencases the optical device 300. The anchor contacts may providestructural support for the layers of the optical device and may work assignal routers to connect the first and second metal layers 332 to thecoupling electrodes 307 and 309.

FIG. 4 is a graph 400 of absorption of incident light 301 on the opticaldevice 300, in accordance with various examples. In the graph 400, thex-axis represents a frequency range of the incident light 301 and they-axis represents the absorption values of incident light 301. Theabsorption values reflect the amplitude of the absorbed light at theplasmonic metasurface 310 as a percentage. The frequency range of thex-axis is represented in terahertz (THz), which corresponds to the IRspectrum. The light absorption is represented by a curve 401 that showspercentages of the absorbed light at the plasmonic metasurface 310within the frequency range. The frequency range of light absorption mayinclude a resonance frequency (ω₀) of the plasmonic metasurface 310. Theabsorbed light in this frequency range may be converted via thepiezoelectric layer 330 into electric energy which can be measured as avoltage 311.

FIG. 5 is a graph 500 of measured voltage responsive to incident light301 on the optical device 300, in accordance with various examples. Insome examples, the voltage 311 is measured at the piezoelectric layer330. In the graph 500, the x-axis represents time in units ofmilliseconds (ms) and the y-axis represents a relative scale of theamplitude values of the measured voltage in units of volts (V). Themeasured voltage is represented by a modulated voltage signal 501 thatincludes the voltage values over a time range. The modulated voltagesignal 501 may be measured responsive to absorbing, at the plasmonicmetasurface 310, the incident light 301, which may be modulated in time.Accordingly, the modulated voltage signal 501 may vary periodically intime between two values having a voltage difference (ΔV) proportional tothe amplitude value of the absorbed light at wo, as described above withrespect to FIG. 4 .

FIGS. 6A and 6B show a top view and a cross section view, respectively,of an optical device 600 including multiple sensor units, in accordancewith various examples. The optical device 600 may include a referencesensor unit 610, a first sensor unit 620, a second sensor unit 630, anda first surrounding surface 642 on a second surrounding surface 644,which is disposed on a substrate 650. The reference sensor unit 610, thefirst sensor unit 620 and the second sensor unit 630 may be separated bya gap 660 from the substrate 650. The gap 660 may provide thermalisolation between the reference sensor unit 610, the first sensor unit620, the second sensor unit 630, and the substrate 650.

Each one of the reference sensor unit 610, the first sensor unit 620,and the second sensor unit 630 may correspond to a separate surface ofthe optical device 600. The reference sensor unit 610, first sensor unit620, and second sensor unit 630 enable the optical device 600 to absorbincident light 301 on the surface of the optical device 300 at multiplefrequency or wavelength ranges, each corresponding to one of thereference sensor unit 610, first sensor unit 620, and second sensor unit630. For example, the light beam 134 may be emitted from the lightsource 110 having a frequency spectrum in the IR region and may bemodulated in time by varying the power of the light source 110. Theoptical device 600 may be part of the optical detector 120 and mayprovide an electrical signal responsive to the optical device 600absorbing the portion of the light beam 134 at the multiple wavelengthranges.

The reference sensor unit 610, the first sensor unit 620, and the secondsensor unit 630 may have a rectangle or square surface geometry. Inother examples, the reference sensor unit 610, the first sensor unit620, and the second sensor unit 630 may have other surface geometries.The reference sensor unit 610 may include a reference sensor unitsurface 662, a reference sensor unit piezoelectric layer 663, a firstreference sensor unit metal layer 664 between the reference sensor unitsurface 662 and the reference sensor unit piezoelectric layer 663, and asecond reference sensor unit metal layer 665 on the gap 660 facingsurface of the reference sensor unit piezoelectric layer 663. Thereference sensor unit surface 662 may include a uniform metal surface666 on a reference sensor unit dielectric layer 667. The first sensorunit 620 may include a first plasmonic metasurface 672, a first sensorunit piezoelectric layer 673, a first sensor unit first metal layer 674between the first plasmonic metasurface 672 and the first sensor unitpiezoelectric layer 673, and a first sensor unit second metal layer 675on the gap 660 facing surface of the first sensor unit piezoelectriclayer 673. The first plasmonic metasurface 672 may include a first 2Darray of first structures 676 on a first sensor unit dielectric layer677. The second sensor unit 630 may include a second plasmonicmetasurface 682, a second sensor unit piezoelectric layer 683, a secondsensor unit first metal layer 684 between the second plasmonicmetasurface 682 and the second sensor unit piezoelectric layer 683, anda second sensor unit second metal layer 685 on the gap 660 facingsurface of the second sensor unit piezoelectric layer 683. The secondplasmonic metasurface 682 may include a second 2D array of secondstructures 686 on a second sensor unit dielectric layer 687. The firststructures 676 and second structures 686 may have patterns of variousgeometries and sizes. For example, the first structures 676 and secondstructures 686 may be square patches. The spacing between the patches ofthe first structures 676 and second structures 686 may be different,causing a different resonance response and resonance frequency forabsorbing the incident light 301 in the IR spectrum.

The uniform metal surface 666 of the reference sensor unit 610 may nothave a resonance response for absorbing the incident light 301 around aresonance frequency, and may have lower absorption than the firstplasmonic metasurface 672 of the first sensor unit 620 and the secondplasmonic metasurface 682 of the second sensor unit 630. Therefore, thereference sensor unit 610 may be useful to detect a base absorptionlevel of incident light 301 as a reference level to the absorptionlevels of the first sensor unit 620 and the second sensor unit 630.

The first surrounding surface 642, the reference sensor unit dielectriclayer 667, the first sensor unit dielectric layer 677, and the secondsensor unit dielectric layer 687 may include the same dielectric layer.The second surrounding surface 644, the reference sensor unitpiezoelectric layer 663, the first sensor unit piezoelectric layer 673,and the second sensor unit piezoelectric layer 683 may include the samepiezoelectric layer. The reference sensor unit 610, the first sensorunit 620, and the second sensor unit 630 may be separated from the firstsurrounding surface 642, and second surrounding surface 644 on thesubstrate 650 by gaps 660 etched in the layers of the optical device600. This separation may provide thermal isolation between the referencesensor unit 610, the first sensor unit 620, the second sensor unit 630,and the surrounding components and layers on the substrate 650.

The reference sensor unit 610 may be anchored to the first surroundingsurface 642 and the second surrounding surface 644 through two contacts691 on opposite sides of the reference sensor unit 610. The contacts 691may be composed of the reference sensor unit dielectric layer 667 andthe reference sensor unit piezoelectric layer 663, which extend from thereference sensor unit 610 to the first surrounding surface 642 and thesecond surrounding surface 644. Similarly, the first sensor unit 620 maybe anchored to the first surrounding surface 642 and the secondsurrounding surface 644 through two contacts 692 on opposite sides ofthe first sensor unit 620. The contacts 692 may be composed of the firstsensor unit dielectric layer 677 and the first sensor unit piezoelectriclayer 673, which extend from the first sensor unit 620 to the firstsurrounding surface 642 and the second surrounding surface 644. Thesecond sensor unit 630 may be anchored to the first surrounding surface642 and the second surrounding surface 644 through two contacts 693 onopposite sides of the second sensor unit 630. The contacts 693 may becomposed of the second sensor unit dielectric layer 687 and the secondsensor unit piezoelectric layer 683, which extend from the second sensorunit 630 to the first surrounding surface 642 and the second surroundingsurface 644.

FIGS. 7A and 7B show a top view and a cross section view, respectively,of an optical device 700 that includes multiple sensor units, inaccordance with various examples. The sensor units may correspond toseparate surfaces which enable the optical device 700 to absorb incidentlight on the surface of the optical device 700 at multiple frequency orwavelength ranges. For example, the optical device 700 may be part ofthe optical detector 120 and may provide an electrical signal responsiveto the optical device 700 absorbing the incident light 301 at themultiple wavelength ranges. The incident light 301 may be a portion ofthe light beam 134 emitted from the light source 110 having a frequencyspectrum in the IR region and may be modulated in time by varying thepower of the light source 110.

The optical device 700 may include multiple layers and materials similarto the optical device 600. The optical device 700 may include areference sensor unit 710, a first sensor unit 720, a second sensor unit730, and a first surrounding surface 742 on a second surrounding surface743, which is disposed on a substrate 744. As shown in FIGS. 7A and 7B,the reference sensor unit 710, the first sensor unit 720, and the secondsensor unit 730 are separated by a first surrounding surface 742 and asecond surrounding surface 743. The reference sensor unit 710, the firstsensor unit 720, and the second sensor unit 730 may also be separated byrespective gaps 745, 746, and 747 from the substrate 744. The gaps 745,746, and 747 may provide thermal isolation between the reference sensorunit 710, the first sensor unit 720, the second sensor unit 730, and thesubstrate 744.

The reference sensor unit 710, the first sensor unit 720, and the secondsensor unit 730 may have a rectangle or square surface geometry. Inother examples, the sensor units may have other surface geometries. Thereference sensor unit 710 may include a reference sensor unit surface762, a reference sensor unit piezoelectric layer 763, a first referencesensor unit metal layer 764 between the reference sensor unit surface762 and the reference sensor unit piezoelectric layer 763, and a secondreference sensor unit metal layer 765 on the gap 745 facing surface ofthe reference sensor unit piezoelectric layer 763. The reference sensorunit surface 762 may include a uniform metal surface 766 on a referencesensor unit dielectric layer 767. The first sensor unit 720 may includea first plasmonic metasurface 772, a first sensor unit piezoelectriclayer 773, a first sensor unit first metal layer 774 between the firstplasmonic metasurface 772 and the first sensor unit piezoelectric layer773, and a first sensor unit second metal layer 775 on the gap 746facing surface of the first sensor unit piezoelectric layer 773. Thefirst plasmonic metasurface 772 may include a first 2D array of firststructures 776 on a first sensor unit dielectric layer 777. The secondsensor unit 730 may include a second plasmonic metasurface 782, a secondsensor unit piezoelectric layer 783, a second sensor unit first metallayer 784 between the second plasmonic metasurface 782 and the secondsensor unit piezoelectric layer 783, and a second sensor unit secondmetal layer 785 on the gap 747 facing surface of the second sensor unitpiezoelectric layer 783. The second plasmonic metasurface 782 mayinclude a second 2D array of second structures 786 on a second sensorunit dielectric layer 787. The first structures 776 and secondstructures 786 may have patterns of various geometries and sizes. Forexample, the first structures 776 and second structures 786 may besquare patches. The spacing between the patches in first structures 776and second structures 786 may be different, causing a differentresonance response and resonance frequency for absorbing the incidentlight 301 in the IR spectrum.

The uniform metal surface 766 of the reference sensor unit 710 may nothave a resonance response for absorbing the incident light 301 around aresonance frequency, and may have lower absorption than the firstplasmonic metasurface 772 of the first sensor unit 720 and the secondplasmonic metasurface 782 of the second sensor unit 730. Therefore, thereference sensor unit 710 may be useful to detect a base absorptionlevel of incident light 301 as a reference level to the absorptionlevels of the first sensor unit 720 and the second sensor unit 730.

The first surrounding surface 742, the reference sensor unit dielectriclayer 767, the first sensor unit dielectric layer 777, and the secondsensor unit dielectric layer 787 may be composed of the same dielectriclayer. The second surrounding surface 743, the reference sensor unitpiezoelectric layer 763, the first sensor unit piezoelectric layer 773,and the second sensor unit piezoelectric layer 783 may be a same (e.g.,contiguous) piezoelectric layer. As shown in FIG. 7A, the sides of thereference sensor unit 710, the first sensor unit 720, and the secondsensor unit 730 may be separated from the first surrounding surface 742and second surrounding surface 743 by gaps 745, 746, and 747 etched inthe layers of the optical device 700, which may provide thermalisolation between the reference sensor unit 710, the first sensor unit720, the second sensor unit 730, and the surrounding components andlayers on the substrate 744.

Each of the reference sensor unit 710, the first sensor unit 720, andthe second sensor unit 730 in the optical device 700 may be anchored byfour contacts on four sides of the sensor units. The reference sensorunit 710 may be anchored to the first surrounding surface 742 and thesecond surrounding surface 743 through four contacts 791 on four sidesof the reference sensor unit 710. The contacts 791 may include thereference sensor unit dielectric layer 767 and the reference sensor unitpiezoelectric layer 763, which extend from the reference sensor unit 710to the first surrounding surface 742 and the second surrounding surface743. Similarly, the first sensor unit 720 may be anchored to the firstsurrounding surface 742 and the second surrounding surface 743 throughfour contacts 792 on four sides of the first sensor unit 720. Thecontacts 792 may include the first sensor unit dielectric layer 777 andthe first sensor unit piezoelectric layer 773, which extend from thefirst sensor unit 720 to the first surrounding surface 742 and thesecond surrounding surface 743. The second sensor unit 730 may also beanchored to the first surrounding surface 742 and the second surroundingsurface 743 through four contacts 793 on four sides of the second sensorunit 730. The contacts 793 may include the second sensor unit dielectriclayer 787 and the second sensor unit piezoelectric layer 783, whichextend from the second sensor unit 730 to the first surrounding surface742 and the second surrounding surface 743.

FIG. 8 is a graph 800 of absorption of incident light on an opticaldevice including multiple sensor units, such as the optical device 600or the optical device 700, in accordance with various examples. In FIG.8 , the x-axis represents a frequency range of the incident light andthe y-axis represents the absorption values of incident light. Theabsorption values reflect the amplitude of the absorbed light at thesensor units of the optical device as a percentage. The frequency rangeof the x-axis is represented in THz, which corresponds to the IRspectrum. The sensor units of the optical device may include a referencesensor unit, a first plasmonic metasurface and a second plasmonicmetasurface. For example, the sensor units may correspond to thereference sensor unit 610, the first sensor unit 620, and the secondsensor unit 630, or may correspond to the reference sensor unit 710, thefirst sensor unit 720, and the second sensor unit 730. The lightabsorption is represented by the curves 801, 802, and 803 that showpercentages of the absorbed light at the surfaces of the referencesensor unit, the first plasmonic metasurface, and the second plasmonicmetasurface, respectively.

The curve 801 shows an absence of a peak in absorption in the frequencyrange, which may be caused by the absence of a resonance response forlight absorption at the reference sensor unit of the optical device. Thecurve 802 shows a peak in absorption in the frequency range at a firstresonance frequency (ω₁) of the first plasmonic metasurface of theoptical device. The curve 803 shows a second peak in absorption in thefrequency range at a second resonance frequency (ω₂) of the secondplasmonic metasurface of the optical device. The first and secondresonance frequencies may be useful for detecting two samples with abroadband IR light source. The peaks in absorptions in the curves 802and 803 of the first and second plasmonic metasurfaces may be atapproximately equal amplitude percentages (as shown in FIG. 8 ) or maybe at different amplitude levels above the reference level in curve 801.The absorption percentages in the curve 801 may be useful as a referencelevel for light absorption compared to the absorption percentages in thecurves 802 and 803. Because the measured voltages responsive to lightabsorption at the reference sensor unit 610 or 710, the first sensorunit 620 or 720, and the second sensor unit 630 or 730 in the opticaldevice 600 or 700 may be proportional to light absorption at the sensorunits, the measured voltage for the reference sensor unit 610 or 710 mayalso be used as a base voltage level to the measured voltages for thefirst sensor unit 620 or 720 and second sensor unit 630 or 730.Accordingly, a relative voltage value may be calculated for each of thefirst sensor unit 620 or 720 and the second sensor unit 630 or 730 withrespect to the measured base voltage for the reference sensor unit 610or 710. The relative voltage values may be useful to quantify therespective amount of light absorption at the first plasmonic metasurface672 or 772 and the second plasmonic metasurface 682 or 782.

FIG. 9 is a diagram of a cross section 900 of a sensor unit 910 anchoredat two opposite sides, in accordance with various examples. In FIG. 9 ,the x-axis represents a length or width of the sensor unit 910 in μm,and the y-axis represents the depth or thickness in μm. The sensor unit910 may have a rectangle or square or other surface geometry with foursides and may be anchored by two contacts 920 coupled to two oppositesides of the four sides. The cross section 900 shows one of the contacts920 on one side of the sensor unit 910. For example, the sensor unit 910may be any of the reference sensor unit 610, first sensor unit 620, orsecond sensor unit 630 in the optical device 600 that is anchoredthrough two corresponding contacts 691, 692, or 693 to the surroundingsurfaces 642, 644 on the substrate 650. FIG. 9 shows a bending in thesensor unit 910 responsive to a deformation across the piezoelectric anddielectric layers that form the sensor unit 910. The contracting andexpanding movement of the piezoelectric layer may be responsive toabsorbing a time modulated incident light on the sensor unit 910.

FIG. 10 is a graph 1000 of voltage to temperature sensitivity of thesensor unit 910 of FIG. 9 , in accordance with various examples. In thegraph 1000, the x-axis represents a measured voltage in units of V andthe y-axis represents the detectable temperature change (ΔT) in kelvin(K). The voltage-to-temperature sensitivity of the sensor unit 910 isrepresented by a curve 1010 that relates V to ΔT for the piezoelectriclayer of the sensor unit 910. ΔT may be proportional to the absorbedlight energy in the sensor unit 910. The slope of the curve 1010 may beuseful as a metric for quantifying the voltage-to-temperaturesensitivity of the piezoelectric layer in the sensor unit 910.

FIG. 11 is a diagram of a cross section 1100 of a sensor unit 1110anchored at four sides, in accordance with various examples. In FIG. 11, the x-axis represents a length or width of the sensor unit 1110 in μmand the y-axis represents the depth or thickness in μm. The sensor unit1110 may have a rectangle or square or other surface geometry with foursides and may be anchored by four contacts 1120 coupled to the foursides. The cross section 1100 shows two of the four contacts 1120 on twoopposite sides of the sensor unit 1110. In various examples, the sensorunit 1110 may be any of the reference sensor unit 710, first sensor unit720, or second sensor unit 730 of the optical device 700 that isanchored through four corresponding contacts 791, 792, or 793 to thesurrounding surfaces 742, 743 on the substrate 744. FIG. 11 showsthickness expansion in the sensor unit 1110 responsive to absorbing thelight energy. In comparison to the sensor unit 910 that is anchored withtwo contacts 920 on two opposite sides, the sensor unit 1110 may exhibitreduced bending responsive to absorbing the light energy, and thusprovide more stability, as a result of its anchoring with the fourcontacts 1120 on the four sides of the sensor unit 1110.

FIG. 12 is a graph 1200 of voltage to temperature sensitivity of thesensor unit 1110 of FIG. 11 , in accordance with various examples. Inthe graph 1200, the x-axis represents a measured voltage in units of V,and the y-axis represents ΔT in K. The voltage-to-temperaturesensitivity of the sensor unit 1110 is represented by a curve 1210 thatrelates V to ΔT for the sensor unit 1110. ΔT may be proportional to theabsorbed light energy in the sensor unit 1110. The slope of the curve1210 may be useful as a metric for quantifying thevoltage-to-temperature sensitivity of the sensor unit 1110. Incomparison to the curve 1010 for the sensor unit 910, the curve 1210 forthe sensor unit 1110 shows increased voltage-to-temperature sensitivityresponsive to the increase in number of contacts 1120 for anchoring andresultant thickness expansion of the sensor unit 1110. The increasednumber of contacts 1120 for anchoring the sensor unit 1110 may increasethermal coupling and reduce thermal isolation with the surroundinglayers.

FIG. 13 is a circuit diagram of an optical detector system 1300including multiple sensor units 1310, in accordance with variousexamples. The multiple sensor units 1310 may be combined in an opticaldevice 1311 of the optical detector system 1300. The optical device 1311may be enabled to absorb and detect an incident light beam, such as forcharacterizing one or more samples, in accordance with the examplesdescribed above. For example, the optical detector system 1300 may bepart of or correspond to the optical detector 120 in the light detectorsystem 100. The optical detector system 1300 may include a multiplexer1312 (MUX) coupled to the multiple sensor units 1310 through respectivetransimpedance amplifiers 1320, a controller 1322 coupled to themultiplexer 1312 through an analog-to-digital converter (ADC) 1340 andan antenna 1360 coupled to the controller 1322.

Each sensor unit 1310 may absorb incident light on the surface of theoptical device 1311 in the optical detector system 1300 within afrequency or wavelength range, as described in the examples above. Forexample, the sensor unit 1310 may be one of the reference sensor unit610, first sensor unit 620, or second sensor unit 630 in the opticaldevice 600, or one of the reference sensor unit 710, first sensor unit720, or second sensor unit 730 in the optical device 700. Each sensorunit 1310 may include a plasmonic metasurface, a piezoelectric layer,and one or more metal layers coupled to the piezoelectric layer.

The transimpedance amplifier 1320 may provide high-to-low impedancetransformation to maintain or amplify the voltage level collected fromthe respective sensor unit 1310 to a voltage level detectable by othercomponents of the optical detector system 1300. The combination of thetransimpedance amplifier 1320 and the respective sensor unit 1310 maymodel an amplifier circuit 1370 with multiple capacitance sources. Forexample, the modeled amplifier circuit 1370 may include a current source1371 representing the current flow from the sensor unit 1310, a firstcapacitor 1372 representing sensor unit intrinsic capacitance, a secondcapacitor 1373 representing parasitic capacitance, and a third capacitor1374 representing the input capacitance of the transimpedance amplifier1310. To maintain or increase the measured voltage level from thetransimpedance amplifier 1320, the capacitances of the second capacitor1373 and third capacitor 1374 may be substantially smaller than thecapacitance of the first capacitor 1372 in the modeled amplifier circuit1370.

The multiplexer 1312 may collect the amplified voltage levels from therespective sensor units 1310 via the respective transimpedanceamplifiers 1320, multiplex the voltage signals in a time sequence andsend the signals as an analog electric signal to the ADC 1340. The ADC1340 may convert the analog electric signal from the multiplexer 1312into a digital signal that can be processed by the controller 1322. Thecontroller 1322 may receive and process the signal to detect theamplitude of absorbed light in the sensor units 1310 and determine thecharacteristics of the one or more samples. The controller 1322 maydetermine which sensor unit 1310 will be read at each time by selectingthe corresponding input in the multiplexer 1312 and may provide timemodulation of the light source 110. The antenna 1360 may establishwireless connections to enable the controller 1322 to send or receivesignals. For example, the optical detector system 1300 may be astand-alone or mountable device that detects light, measures a resultingvoltage, characterizes a sample accordingly, and sends the data in awireless connection to a central device or system (not shown). In otherexamples, the optical detector system 1300 may detect light, measure aresulting voltage, and send this information to another device or system(not shown) for analysis.

FIG. 14 is a graph 1400 of multiple light absorption profiles for anoptical device including multiple sensor units, in accordance withvarious examples. In the graph 1400, the x-axis represents a range ofwavelengths of the incident light in nanometers (nm) and the y-axisrepresents the absorption values of incident light. The absorptionvalues reflect the amplitude of the absorbed light at the multiplesensor units of the optical device as a percentage. The wavelength rangeis between approximately 7000 and 12000 nm, which corresponds to the IRspectrum for a broadband light source. The graph 1400 shows the lightabsorption profiles represented by curves 1401, 1402, and 1403 for threerespective sensor units 1410, 1420, and 1430, which may be combined inan optical detector. For example, the sensor units 1410, 1420, and 1430may be combined in the optical detector 120 of the light detector system100 or in the optical detector system 1300. The sensor units 1410, 1420,and 1430 may be configured similar to the reference sensor unit 610, thefirst sensor unit 620, and the second sensor unit 630, respectively, inthe optical device 600 or the reference sensor unit 710, the firstsensor unit 720, and the second sensor unit 730, respectively, in theoptical device 700. Each sensor unit 1410, 1420, and 1430 includes aplasmonic metasurface designed to absorb light at a certain resonancefrequency or wavelength.

The curves 1401, 1402, and 1403 represent the resonance responses forthe sensor units 1410, 1420, and 1430, respectively. The curves 1401,1402, and 1403 show percentages of the absorbed light at the plasmonicmetasurfaces of the sensor units 1410, 1420, and 1430 in the IRwavelength range of the broadband light source. The resonance responsesof the sensor units 1410, 1420, and 1430 include three resonancewavelengths at approximately 9300 nm, 9900 nm, and 10800 nm,respectively. By integrating the three sensor units 1410, 1420, and 1430in the optical device, the resonance response, and therefore thedetection capability of the optical detection system, can be increasedto multiple types of samples over a broadband spectrum.

FIG. 15 is a flow diagram of a method 1500 for light detection in anoptical device, in accordance with various examples. The optical devicemay include a plasmonic metasurface, a piezoelectric layer, and one ormore metal layers coupled to the piezoelectric layer. For example, themethod 1500 may be performed by a light detector system such as thelight detector system 100 or the optical detector system 1300. The lightdetector system may include an optical device such as the opticaldevices 300, 600, or 700, or another optical device designed inaccordance with the optical devices described above. At step 1501, alight source having a frequency spectrum may be modulated in time. Forexample, the frequency spectrum of the emitted light may be an IRspectrum or a visible light spectrum. At step 1502, one or moreplasmonic metasurfaces of a light detector system may absorb, at one ormore respective resonance wavelengths of the plasmonic metasurfaces, thelight emitted by the light source that strikes the plasmonicmetasurfaces as incident light. The one or more plasmonic metasurfacesmay correspond to one or more sensor units in the optical device and mayeach absorb a portion of the incident light within a correspondingresonance wavelength range. At step 1503, an amplitude of a voltageacross a piezoelectric layer of the light detector may be measured. Themeasured voltage may be modulated in time in accordance with themodulated incident light on the optical device. The piezoelectric layermay be coupled to the one or more plasmonic metasurfaces and may convertthe energy of the absorbed light into a measurable voltage. The voltagemay be measured in one or more sensor units with a time multiplexingscheme. At step 1504, an amplitude of the voltage, and accordingly acorresponding change in the intensity of the incident light, may bedetermined. The light intensity may be determined based on the amplitudeand analyzed by a microprocessor or a processing system to infercharacteristics of one or more samples exposed to the light beam afteremission by the light source and before absorption of light by theoptical device.

FIG. 16 is a block diagram of a hardware architecture 1600 of aprocessing system, in accordance with various examples. The hardwarearchitecture 1600 includes hardware components that may be part of theprocessing system. For example, the hardware architecture 1600 maycorrespond to the processing system 150 in the light detector system100. As shown in FIG. 16 , the hardware architecture 1600 may includeone or more processors 1601 and one or more memories 1602. In someexamples, the hardware architecture 1600 may also include one or moretransceivers 1603 and one or more antennas 1604 for establishingwireless connections. These components may be connected through a bus1605 or in any other suitable manner. In FIG. 16 , an example in whichthe components are connected through a bus 1605 is shown.

The processor 1601 may be configured to read and executecomputer-readable instructions. For example, the processor 1601 may beconfigured to invoke and execute instructions stored in the memory 1602,including the instructions 1606. The processor 1601 may support one ormore global systems for wireless communication. Responsive to theprocessor 1601 sending a message or data, the processor 1601 drives orcontrols the transceiver 1603 to perform the sending. The processor 1601also drives or controls the transceiver 1603 to perform receiving,responsive to the processor 1601 receiving a message or data. Therefore,the processor 1601 may be considered as a control center for performingsending or receiving, and the transceiver 1603 is an executor forperforming the sending and receiving operations.

In an example, the memory 1602 may be coupled to the processor 1601through the bus 1605 or an input/output port. In another example, thememory 1602 may be integrated with the processor 1601. The memory 1602is configured to store various software programs and/or multiple groupsof instructions, including instructions 1606. For example, the memory1602 may include a high-speed random-access memory and may include anonvolatile memory such as one or more disk storage devices, a flashmemory, or another nonvolatile solid-state storage device. The memory1602 may store an operating system such as ANDROID, IOS, WINDOWS, orLINUX. The memory 1602 may further store a network communicationsprogram. The network communications program is useful for communicationwith one or more attached devices, one or more user equipment, or one ormore network devices, for example. The memory 1602 may further store auser interface program. The user interface program may display contentof an application through a graphical interface, and receive a controloperation performed by a user on the application via an input controlsuch as a menu, a dialog box, or a physical input device (not shown).The memory 1602 may be configured to store the instructions 1606 forimplementing the various methods and processes provided in accordancewith the various examples of this application.

The antenna 1604 may be configured to convert electromagnetic energyinto an electromagnetic wave in free space or convert an electromagneticwave in free space into electromagnetic energy in a transmission line.The transceiver 1603 may be configured to transmit a signal that isprovided by the processor 1601 or may be configured to receive awireless communications signal received by the antenna 1604. In thisexample, the transceiver 1603 may be considered a wireless transceiver.

The hardware architecture 1600 may also include another communicationscomponent such as a Global Positioning System (GPS) module, a BLUETOOTHmodule, or a WI-FI module. The hardware architecture 1600 may alsosupport another wireless communications signal such as a satellitesignal or a short-wave signal. The hardware architecture 1600 may alsobe provided with a wired network interface or a local area network (LAN)interface to support wired communication.

In accordance with various examples, the hardware architecture 1600 mayfurther include an input/output device (not shown), such as an audioinput/output device, a key input device, a display, and the like. Theinput/output device may be configured to implement interaction betweenthe hardware architecture 1600 and a user/an external environment, andmay include the audio input/output device, the key input device, thedisplay, and the like. The input/output device may further include acamera, a touchscreen, a sensor, and the like. The input/output devicemay communicate with the processor 1601 through a user interface.

The hardware architecture 1600 shown in FIG. 16 is a possibleimplementation in various examples of this application. During actualapplication, the hardware architecture 1600 may include more or fewercomponents. This is not limited herein.

The term “couple” is used throughout the specification. The term maycover connections, communications or signal paths that enable afunctional relationship consistent with this description. For example,if device A provides a signal to control device B to perform an action,in a first example device A is coupled to device B or in a secondexample device A is coupled to device B through intervening component Cif intervening component C does not substantially alter the functionalrelationship between device A and device B such that device B iscontrolled by device A via the control signal provided by device A.

A device that is “configured to” perform a task or function may beconfigured (e.g., programmed and/or hardwired) at a time ofmanufacturing by a manufacturer to perform the function and/or may beconfigurable (or reconfigurable) by a user after manufacturing toperform the function and/or other additional or alternative functions.The configuring may be through a construction and/or layout of hardwarecomponents and interconnections of the device, or a combination thereof.

A device that is described herein as including certain components mayinstead be adapted to be coupled to those components to form thedescribed device. For example, a structure described as including one ormore elements (such as structures or layers) and/or one or more sources(such as voltage and/or current sources) may instead include only theelements within a single physical device (e.g., the structures andlayers in the device) and may be adapted to be coupled to at least someof the sources to form the described structure or system either at atime of manufacture or after a time of manufacture, such as by anend-user and/or a third-party.

While certain components may be described herein as being of aparticular process technology, these components may be exchanged forcomponents of other process technologies. Structures and designsdescribed herein are reconfigurable to include the replaced componentsto provide functionality at least partially similar to functionalityavailable prior to the component replacement.

Unless otherwise stated, “about,” “approximately,” or “substantially”preceding a value means+/−10 percent of the stated value. Modificationsare possible in the described examples, and other examples are possiblewithin the scope of the claims.

What is claimed is:
 1. An apparatus, comprising: a first metal layer; apiezoelectric layer on the first metal layer; a second metal layer onthe piezoelectric layer; a plasmonic metasurface on the second metallayer, wherein the plasmonic metasurface comprises a dielectric layerand metal structures; and a voltage detector coupled to the first metallayer and the second metal layer
 2. The apparatus of claim 1, whereinthe metal structures are embedded in or positioned on the dielectriclayer.
 3. The apparatus of claim 1, further comprising a first anchorcontact and a second anchor contact on opposite sides of the plasmonicmetasurface, wherein the first anchor contact and the second anchorcontact comprise respective extensions of the first metal layer, thepiezoelectric layer, the second metal layer, and the dielectric layer.4. The apparatus of claim 3, further comprising a third anchor contactand a fourth anchor contact on opposite sides of the plasmonicmetasurface, wherein the first anchor contact, the second anchorcontact, the third anchor contact, and the fourth anchor contact are onfour different sides of the plasmonic metasurface.
 5. The apparatus ofclaim 1, wherein the metal structures are metal patches that are equallyspaced in a two-dimensional grid formation, and wherein a size and aspacing of the metal structures are configured to cause absorption of anincident light at a frequency range narrower than a frequency spectrumof the incident light.
 6. The apparatus of claim 1, wherein thepiezoelectric layer includes aluminum nitride, and wherein thedielectric layer includes silicon oxide.
 7. The apparatus of claim 1,further comprising: a substrate coupled to a first portion of thepiezoelectric layer; and a gap disposed between the substrate and eitherthe first metal layer or a second portion of the piezoelectric layer. 8.The apparatus of claim 1, further comprising: a first electrode coupledto the voltage detector and the first metal layer; and a secondelectrode coupled to the voltage detector and the second metal layer. 9.An optical device, comprising: a plasmonic metasurface configured toabsorb an incident light having a frequency spectrum, wherein theincident light is modulated in time; a first metal layer coupled to theplasmonic metasurface; a piezoelectric layer coupled to the first metallayer; a second metal layer coupled to the plasmonic metasurface; and avoltage detector coupled to the first metal layer and second metallayer, the voltage detector configured to detect an amplitude of anelectrical signal modulated in time according to the modulated incidentlight.
 10. The optical device of claim 9, wherein the frequency spectrumof the incident light is an infrared (IR) spectrum of light.
 11. Theoptical device of claim 9, further comprising a processor coupled to thevoltage detector and configured to determine a change in the amplitudeof the modulated electrical signal and a change in a temperature of thepiezoelectric layer, wherein the change is proportional to the incidentlight absorbed at the plasmonic metasurface at a wavelength range withinthe frequency spectrum.
 12. The optical device of claim 11, wherein theprocessor is configured to: determine a change in intensity of theincident light based on the change in the amplitude of the electricalsignal; and obtain a characteristic of a gas or fluid exposed to theincident light based on the change in the intensity of the incidentlight.
 13. A light detector system, comprising: a light sourceconfigured to emit light having a frequency spectrum, wherein the lightis modulated in time; and an optical detector configured to detect anintensity of the light at a wavelength range within the frequencyspectrum, wherein the optical detector comprises: a piezoelectric layer;a first metal layer coupled to a first surface of the piezoelectriclayer; a second metal layer coupled to a second surface of thepiezoelectric layer; a plasmonic metasurface coupled to the first metallayer and configured to absorb the light at the wavelength range,wherein the plasmonic metasurface comprises metal structures and adielectric layer disposed on the first metal layer; and a voltagedetector coupled to the first metal layer and the second metal layer,the voltage detector configured to detect a voltage at a frequency ofthe modulated light.
 14. The light detector system of claim 13, furthercomprising a chamber between the light source and the optical detector,the chamber configured to contain a gas or a fluid and to allow thelight to propagate through the chamber from the light source to theoptical detector.
 15. The light detector system of claim 13, furthercomprising a processor adapted to be coupled to the voltage detector,the processor configured to determine an amplitude of the voltage at thefrequency of the modulated light, a change in the amplitude of thevoltage, and a change in the intensity of the light based on the changein the voltage.
 16. The light detector system of claim 15, wherein theplasmonic metasurface is a first plasmonic metasurface, and the lightdetector system further comprises a second plasmonic metasurface coupledto the first metal layer and configured to absorb the light at a secondwavelength range within the frequency spectrum, and wherein the secondplasmonic metasurface comprises second metal structures disposed on thedielectric layer.
 17. The light detector system of claim 16, wherein themetal structures of the plasmonic metasurface are first metal patchesequally spaced in a first two-dimensional grid formation and having afirst size and a first spacing, and wherein the second metal structuresof the second plasmonic metasurface are second metal patches equallyspaced in a second two-dimensional grid formation and having a secondsize and a second spacing.
 18. The light detector system of claim 17,further comprising a reference detection layer coupled to the firstmetal layer, the reference detection layer comprising a uniform metallayer disposed on the dielectric layer.
 19. The light detector system ofclaim 18, further comprising: a multiplexer adapted to be coupled to thereference detection layer, the plasmonic metasurface, and the secondplasmonic metasurface through respective amplifier circuits; and ananalog-to-digital converter (ADC) adapted to be coupled to themultiplexer and the processor.
 20. The light detector system of claim19, wherein the respective amplifier circuits include a firsttransimpedance amplifier adapted to be coupled to the referencedetection layer, a second transimpedance amplifier adapted to be coupledto the plasmonic metasurface, and a third transimpedance amplifieradapted to be coupled to the second plasmonic metasurface.